I put the word "some" in front of "crypto" for a reason.
There is some crypto that we know how to break with a sufficiently large quantum computer [0]. There is some we don't know how to do that to. I might be behind the state of the art here, but when I wasn't we specifically really only knew how to use it to break cryptography that Shor's algorithm breaks.
Nope. Any crypto you can break with a real, physical, non-imaginary quantum computer, you can break faster with classical. Get over it. Shor's don't run yet and probably never will.
You are misdirecting and you know it. I don't even need to discredit that paper. Other people have done it for me already.
They can break some cryptography... other than that... what are they good for?
There's some highly speculative ideas about using them for chemistry/biology research, but no guaranteed return on investment at all.
As far as I know... that's it.